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1 March 2015 Preemergence Control of Spotted Spurge ( Chamaesyce maculata) with Flumioxazin as Influenced by Formulation and Activation Moisture
Glenn Wehtje, Q. Yang, Charles H. Gilliam, Anna-Marie Murphy, Jason Fausey
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Flumioxazin is commonly used in nursery production for PRE weed control. Container nursery producers are of the opinion that the granular formulation is less effective than the sprayable formulation. Under the hypothesis that the granular formulation may require more water for activation, an experiment was conducted to evaluate the interaction of flumioxazin formulation, rate, and activation moisture for PRE control of spotted spurge in a pine-bark substrate. Experiment consisted of a factorial arrangement of four experimental variables; flumioxazin formulation (granular and spray), and flumioxazin rate (0.28 and 0.42 kg ai ha−1), substrate moisture level at the time of application (dry, medium, and wet), and after-application irrigation level (a single irrigation at 0.6, 1.3, 2.5, and 5.1 cm). Treated pots were seeded with spotted spurge 2 d after the herbicide application, which was 1 d after the first irrigation. Control as indicated by spotted spurge counts and fresh weight was influenced only by flumioxazin rate and formulation. The sprayable formulation provided excellent control regardless of rate. Granular formulation was generally less effective, and additional activation moisture did not improve efficacy. Further studies were conducted with the granular formulation to determine the maximum separation distance between the spotted spurge seed and herbicide prills at which control is possible. Individual prills and spotted spurge seeds were placed on media surface at progressively increasing separation distances. Nonlinear regression of seedling survival data revealed that ≥99% control required a prill–seed separation of ≤5.2 mm. This prill–seed separation requirement is only marginally obtained with the current registered rate, i.e., 0.42 kg ai ha−1 or 168 kg product ha−1 . The relationship between control and prill–seed separation distance cannot be manipulated by additional activation moisture. Inadequate contact between the spotted spurge seeds and the flumoioxazin-containing prills is likely the sole cause of inadequate control.

Nomenclature: Flumioxazin; spotted spurge, Chamaesyce maculata (L.) Small ‘EPHMA'.

Flumioxazin es comúnmente usado en viveros para el control PRE de malezas. Productores de viveros de plantas en potes son de la opinión de que la formulación granular es menos efectiva que la formulación asperjable. Bajo la hipótesis de que la formulación granular requiere más agua para la activación, se realizó un experimento para evaluar la interacción de la formulación de flumioxazin, la dosis, y la humedad de activación para el control PRE de Chamaesyce maculata en sustrato de corteza de pino. El experimento consistió en una arreglo factorial de cuatro variables experimentales: formulación de flumioxazin (granular y aspersión), y dosis de flumioxazin (0.28 y 0.42 kg ai ha−1), nivel de humedad del sustrato al momento de la aplicación (seco, medio, y mojado), y el nivel de riego después de la aplicación (una sola aplicación a 0.6, 1.3, 2.5, y 5.1 cm). En los potes tratados se sembró C. maculata 2 d después de la aplicación del herbicida, la cual se realizó 1 d después del primer riego. El control de la maleza, determinado mediante conteos de plantas de C. maculata y peso fresco, fue influenciado solamente por la dosis y formulación de flumioxazin. La formulación asperjable brindó excelente control sin importar la dosis. La formulación granular generalmente fue menos efectiva, y la humedad adicional para activación no mejoró la eficacia. Se realizaron estudios adicionales con la formulación granular para determinar la distancia de separación máxima entre la semilla de C. maculata y los grá

Glenn Wehtje, Q. Yang, Charles H. Gilliam, Anna-Marie Murphy, and Jason Fausey "Preemergence Control of Spotted Spurge ( Chamaesyce maculata) with Flumioxazin as Influenced by Formulation and Activation Moisture," Weed Technology 29(1), 108-114, (1 March 2015).
Received: 31 March 2014; Accepted: 1 August 2014; Published: 1 March 2015

herbicide activation
herbicide leaching
herbicide persistence
ornamental plant production
soilless growth media
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